Textile fibrous product



March 15, 1949,

C. S. FRANCIS, JR

TEXTILE FIBROUS PRODUCT 2 Sheets-Sheet 1 Filed Dec. 18, 1943 'ISYSIINVLI-INTOR. CARLETOA/ S. FRANC/S JR.

BY I

ATTORNEY c, s. FRANCIS, JR TEXI-ILE FIBROUS PRODUCT web 15, E949,

2 Sheets-Sheet 2 Filed Dec. 18, 1945 armmmmw,

INVENTOR. CARLETON 6. FRANC/SJA.

ATTORNEY I UNITED STATES PATENT OFFICE Carleton 8. Francis, Jr., WeltHarwlch, Mala, asslgnor to American Viscose Corporation, Wilmington,Del., a corporation of Delaware Application December is, 1943, SerialNo. 514,156

4 Claims. (Cl. 154-46) This invention relates products and to processesof producing fibrous products, particularly of the class of textiles,felts and papers. and to correlated improvements therein designed toenhance the structure, properties and uses of the fibrous products. Thisapplication is a continuation-impart of my pending applications SerialNos. 381,292, March 1, 1941, and 405,102, August 1, 1941, which latterapplication is in turn a continuation-in-part of my copendingapplications Serial Nos. 300,876, October 23, 1939, now Patent No.2,459,803, and 381,292, March 1, 1941, now Patent No. 2,357,392.

In my prior applications there are disclosed various fibrous products,such as felts, papers, and pile fabrics formed from a mixture of atleast two types of fibers, one of the fibers being potentially adhesive,and processes of forming such products by rendering the potentiallyadhesive fibers in the mixture tacky at some stage of the process, tobind fibers in the product.

It is a general object of the presentinvention to provide fibrousproducts consisting entirely of potentially adhesive fibers orcomprising such fibers in admixture with other fibers in which novel andimproved structural characteristics are obtained and if desired, suchcharacteristics may be accompanied by decorative eilects. Furtherobjects and advantages will be apparent from the descriptionhereinafter. v

In. accordance with this invention, fibrous products comprisingpotentially adhesive fibers are fabricated in the same general manner asin my prior applications, with the exception that the activation or thestep of rendering the potentially in general to fibrous or adhesive inthose areas. Such activation may be accompanied by pressure, preferablyapplied at the portions in which activation is eflected. Besides thepossibility of obtaining decorative effects when pressure is utilized,the utilization oi selective activation. with or without pressure isaccompanied by valuable advantages in respec to the structure of,theproducts.

For example, when it is desired to use such felt-like products forfiltration Pu oses, the so lective activation to spot,-weldjthestructure. as it were, 'or to activate a grid of two sets of parallellines intersecting at any desired angle to adhesive fibers tacky iseffected at preselected points or areas of the products ordifferentially therein. Thus, in one embodiment of my invention, a pilefabric is formed by depositing a fiock comprising a mixture ofpotentially adhesive fibers with others of different nature upon a basefabric carrying an adhesive coating. subsequent to the setting of suchadhesive, the pile fabric thus formed may be subjected to an activatingagent and pressure to impart novel decorative effects resulting from theadhesion of fibers in the pile.

In another embodiment of the invention a mass of fibers comprising thepotentially adhesive fibers may be formed by carding or by depositionfrom a fiuid suspension thereof onto a moving band, or by any othersystem into felt-like or paper-like structures, and thereafter suchstructures may be activated in selected portions there of to render thepotentially adhesive fibers tacky increase its structural stability canbe applied without appreciable loss in porosity. 'It is not possible toobtain an equivalent porosity when the felt-like mass is activateduniformly throughout its area to obtain a given structural stability asdetermined by rigidity and "freedom from crushing at the edges whenallowed to8tan'd upright.

In the following specification and in. the claims, the term fiber" or"fibers when used in reference to the potentially adhesive material isintended to include any fibril, fiber, filament or' filamentarystructure, regardless of length or diameter, and whether independent ofone an-. other or adhered together at spaced points to form. a web ofreticulated structure. The expression "matted fibrous structure includeswebs.

mats, bats, pile fabrics. and, other interfelted products. The termadhesive includes sticky, cementitious, agglutinouabr tacky conditions.The term non-adhesive fibers" includes those fibers which, although theymay be rendered adhesive ,by some treatment, are not rendered adhesiveunder the conditions used to activate the potentially adhesive fibersassociatedtherewith .In the drawing illustrative of the invention-Figure 1 is a side elevation, partly in section of one embodiment ofsuitable means for form ing the potentially adhesive fibers used in theinvention;

Figure 2 is a side elevation, partly in section, of one embodiment ofmeans for carrying out the invention in the fabrication of felts andpapers;

Figure 3 is a side elevation, partly in section, of another embodimentfor carrying out the invention;

Figure '4 is a plan view of the modification of Figure 3;

Figure 5 is a perspective view of another em bodiment for carrying outthe invention; Figure 6 is an elevation, partly in section, showinganother embodiment for carrying out the invention;

Figure '7 is a perspective of still another embodiment for carrying outthe invention;

Figure 8 is a cross-section of a. product constituting one form of theinvention;

Figure 9 is a perspective of another such product; and

Figure 10 is a face view of still another such product.

The potentially adhesive fibers may be a, cellulose derivative, a resinor rubber. Among the cellulose derivatives which are suitable are, forexample, cellulose esters, cellulose ethers, mixed celluloseester-ethers, mixed cellulose esters, mixed cellulose ethers, andmixtures of cellulose derivatives. Among the resins which may beemployed for forming the potentially adhesive fibers are, for example,cheap natural resins, such as shellac, damar, copal, and the like, andsynthetic resins formed by the polymerization of various organiccompounds, such as coumarone, indene hydrocarbons, vinyl esters andethers, styrene, sterols, phenol-aldehyde resins, either unmodified ormodified with oils, urea-aldehyde resins, sulfonamide-aldehyde resins,olyhydrie alcoholpolybasic acid resins, drying oil-modified alkydresins, resins formed from acrylic acid, its homologues and theirderivatives, sulfur-olefine resins, resins formed from dicarboxylicacids and diamines (nylon type) synthetic rubbers and rubbersubstitutes, herein called resins, such for example as polymerizedbutadiene, olefine polysulfides, isobutylene polymers, chloroprenepolymers; and fibers formed from a resin comprising the product ofcopolymerizing two or more resins, such as copolymers of vinyl halideand vinyl acetate, copolymers of vinyl halide and an acrylic acidderivative; and also a mixture of resins, such as a mixture of vinylresins and acrylic acid resins or methacrylic acid resins, a mixture ofpolyolefine resins and phenol-aldehyde resins, or a mixture of two ormore resins from the different classes just named. There may be employedalso fibers -made from rubber latex, crepe rubber, gutta percha, balata,and the like.

Further, the potentially adhesive fibers may be mixtures of thecellulose derivatives with resins or rubber, such for example, as amixture of cellulose nitrate and an acrylic acid resin, or a mixture ofbenzyl cellulose and a vinyl resin, or a mixture of ethyl cellulose andshellac.

The resins above mentioned may be classified (a) Heat-non-convertibleresins such as glycol polybasic acid resins, vinyl resins and the acidtype phenol-aldehyde resins, and the like.

(b) Heat convertible (or thermosetting) resins, such as aglycerol-polybasic acid resin, polyolefine resins, phenol aldehyderesins and the like.

An element-convertible resin (which becomes infusible through the actionof certain elements, such as oxygen and sulfur) such asglycerol-polybasic acid-drying oil, resins and .olefine sulfur resins.

Among the non-adhesive fibers which may be employed are natural fibers,such as wood pulp fibers. cotton, flax, jute, kapok, wool, hair andsilk; and synthetic fibers, such as cellulosic fibers, such as cellulosehydrate, or cellulose derivatives, as cellulose esters, mixed celluloseesters, cellulose ethers, mixed cellulose ester-ethers, mixed celluloseethers, cellulose hydroxy-alkyl ethers, cellulose carboxyl alkyl ethers,cellulose ether-xanthates, cellulose xantho-fatty acids. cellulosethiouret-hanes, natural and synthetic rubber and derivatives thereof;fibers made of alginic acid, gelatine, casein; and mineral fibers suchas spun glass, asbestos, mineral wool and the like; and fibers made ofnatural and synthetic resins which are not rendered tacky when thepotentially adhesive resin fibers are rendered tacky; also fibers andfilaments made by slitting, cuttin or shredding non-fibrous films, suchas waste cellophane.

The potentially adhesive fibers may be preformed, for example, byextrusion, or they may be made by dispersing into a fiuid,,a potentiallyadhesive fiber-forming material, as described in my Patent No.2,357,392. By the latter procedure, such materials as are not adapted tothe forming of fibers by extrusion may be utilized, since such factorsas filtering characteristics, solution viscosity and fiber tenacity arenot critical in that process. In order to disperse the fiberformingmaterial into the fluid in accordance with my copending application, thematerial is rendered flowable, i. e., plastic or molten or dissolved ina volatile solvent. To the fiber-forming material or solution thereof,there may be added suitable plasticizers, hardening agents for theresins, latent activating agents, dyes, pigments, moth-proofing agents,fire-proofing agents, waterproofing agents, and the like.

The fiber-forming material or solution thereof may be handled in aconventional type of spray gun, shown in Figure 1 and hereafterdesignated generally by the reference character i, and comprisingessentiallya container 2 adapted to hold the fiber-forming compositionfromwhich it is forced by air pressure through the supply line 3 to thechamber 4 from which the composition is discharged through the orifice5. The air is supplied through the line 6 to the air chamber 1 whichsurrounds the chamber 4 and terminates in a plurality of orifices 8positioned adjacent the orifice 5. The trigger or handle 9 is adaptedtooperate the pin valve I0 which opens the orifice 5 and the air valve Hwhich opens the air line 6. As the stream of fiber-forming compositionis discharged from the orifice 5, it is disrupted into fibers by theforce of the tangential streams of air discharged through the orifices8.

The above-described fiber-forming processes may be employed forproducing the non-adhesive textile or felt fibers as well as thepotentially adhesive fibers.

In Figure 2 there is shown one embodiment of suitable apparatus forforming felt-like mats of the invention. A composition suitable forforming potentially adhesive fibers is dispersed by means of the spraygun I into a heated gaseous atmosphere contained in the chamber 20, intowhich may be simultaneously blown non-adhesive fibers 21 through conduit22 by means of a blower 23, The fibers fall downwardly in the chamberand come to rest on the surface of an endless belt 24 made of porous orperforated flexible material such as textile, metal, leather or thelike, which is positioned in a horizontal plane at the base of thechamber 20. The mat of fibers 281s carried on the belt from the chamberand through pinch rolls 25 and 26 which compress the bat and enable itto be removed from the belt for activating 0r finishing operations to behereinafter described. The solvent evaporated from the fiberformingcomposition may be withdrawn from the chamber 20 through exhaust pipe 21and wasted or recovered'in a known manner. A suction pump endless belt24 as it passes under chamber 20. In the manufacture of paper tissues,the belt 24 may be considered as comprising the wire'screen of thepaper-making machine and the fibers may be deposited from an aqueoussuspension. Thus. the fiber-forming and felting steps in making thefelts and papers are carried out concurrently and continuously, that is,in immediate sequence in a simple and economical manner. In making aninterfelted web containing only potentially adhesive fibers in anapparatus such as shown in Figure 2, the conduit 22 and the blower 23are omitted. If a felt of greater thickness than can be obtained with asingle deposition of fibers is desired, the bat may be built up to thedesired thick ness by repeated passages thereof under chamber 20.

When preformed potentially adhesive fibers are employed in theproduction of the fibrous product, the fibers (cut into suitable lengthfor carding), may be handled in the conventional manner and with thewell-known equipment employed in the production of felt, wherein thefibers are fed into a card and deposited in the form of a web on anendless belt. As is customary, fibers are fed from the card onto thebelt in layers until the desired thickness has been obtained. The bat soformed may be compacted by pressure rolls in order to make the batself-supporting and susceptible to handling. In one embodiment, a minorproportion of non-thermoplastic fibers is blended with the thermoplasticfibers during the carding operation. If, however, it is desirable toutilize nonthermoplastic fibers in conjunction with fibers obtained bydispersion with .a fiuid of a potentially adhesive fiber-formingmaterial, this may be accomplished by forming a carded web of thenonthermoplastic fibers, and during the formation of the bat, thepotentially adhesive fibers may be formed as previously described andcommingled with the other fibers as the layers of the web are built upon the endless belt.

In order to facilitate handling of the bat of .fibers without damagingit, the potentially adhesive fibers are rendered adhesive in selectedareas by heat or solvent to cause at least a partial adhesion betweenthe fibers. Among the methods which may be used for activation are thefollowing, taken singly or together in appropriate com binations.

1. When the potentially adhesive fibers are thermoplastic, they may beactivated by heat applied locally, with or without pressure, as by useof hot water, steam or a blast of dry hot gas, or heated surfaces. J

2. They may be activated by applying locally to the fibrous mixturea'solvent or swelling agent,

or mixtures thereof with diluents under such conditions of concentrationand temperature as to render the potentially adhesive fibers tacky. Forexample, fibers Oforganic cellulose derivatives, such as celluloseesters, may berendered adhesive-by solvents,'such as acetone, ethylacetate, butyl acetate, and the like.

3. A latent activating agentmay be combined with the potentiallyadhesive fibers and/or with the non-adhesive fibers. Such agent may beren dered active by a subsequent treatment applied locally, such aschemical agents, heat or. irradiation, thus producin a simultaneousactivation of the potentially adhesive fibers in selected areas. Forexample, fibers may be impregnated with a liquid which, at roomtemperature, isa non-solvent therefor but which, at a higher or lowertem-' may,function to increase the flexibility of the fibers and, whenemployed with thermoplastic fibers, the plasticizer may serve, inaddition, to lower the thermal softening point. The plasticiz'edthermoplastic fibers can be rendered adhesive by heating to atemperature below that at which the non-thermoplastic textile fibersassociated therewith would be detrimentally affected by such heating.The plasticizer may be allowed to remain in the product, or it may beremoved by suitable means, such as washing and extraction, thus againelevating the thermal softening point of the thermoplastic material andpreventing reactivation upon ironing.

While the fibers are in an adhesive condition, the fibers are preferablysubjected locally to a. compacting treatment to promote adhesion of theassociated fibers at their points of contact and the term compactingincludes pressing, squeezing and tension. For example, mechanicallyapplied pressure may be exerted on the activated material during and/orafter activation, and/or during calendaring, embossing, printing, dryingand other o erations involving the use of rollers.

After activation, the fibrous material is treated to deactivate theadhesive, that is, to render the adhesive non-tacky so as to fix the newrelationship of the fibers. V The nature and extent of the deactivationtreatment will depend, inter alia, upon the nature and extent of theactivating treatment and upon the proportion and kind of potentiallyadhesive fibers used. If activation has been accomplished by heat,deactivation may be accomplished by cooling or, in the case ofthermosetting resin fibers, by heating to a higher temperature; ifactivation is by means of a solvent, deactivation may involve extractionof the solvent by washing, evaporation, decomposition. The removal ofthe activating agent depends upon whether its presence in the product isdesirableor objectionable.

The activating, compacting and deactivating treatments herein describedmay be carried out independently of, or simultaneously with, varioustreatments common to the fabrication and finishing of textiles and feltsor the laminating and sealing of sheet materials.

, extent of activation, compacting and deactivation may be variedconsiderably, depending upon the relative proportions of the types offibers, the properties of the potentially adhesive fibers and the effectdesired in the product. The potentially adhesive fibers may be renderedsuperficially tacky; or made adhesive without losing their fibrous form;or rendered sufilciently fluid to spread under pressure to form a filmin which the other fibers are embedded. If the potentially adhesivefibers are rendered only slightly tacky,

the frictional resistance between fibers will be increased and thestrength improved. If the potentially adhesive fibers are renderedsubstantially adhesive, they will cohere to each other and adhere to theother fibers to fix the position thereof to give a product havingincreased tensile strength, structural stability, and lower stretchandshrinkage. As stated, the amount of potentially adhesive fiberspresent will depend on the characteristics desired in the product. Theproduct may comprise 100% potentially adhesive fibers or the proportionsmay range from as low as about 50% up to 95% or more of the total weightof the fabric.

The fibrous product, whether a pile fabric or of felt-like or paper-likenature, maybesubjected to activation in numerous ways. For example, inFigures 3 and 4, the product is treated locally with an activating agentin fiuid state adapted to render the potentially adhesive fibers tackyor adhesive. As shown, the producg s is laid upon the openings 3! in thetops of tlie hollow conically shaped projections 32 formed on the uppersurface 33 of a container 34. supplied by pump 35 connected to it by theconduit 36. The product A may be held in place merely by gravity, butholding means may be provided for this purpose and any desired pressuremay be applied, if desired. The pump may be operated by hand orautomatically to force a given amount of solvent or stream or dry hotair through the regions of the product above the areas adjacent theopenof rolls 3'! and 38. Roll 38 has a smooth surface but roll 31 isprovided with evenly spaced projections 39 of round cross-section and isheated by steam introduced by an axial pipe 40 of conventionalconstruction. The projections preferably a are of sufficient height thatthe peripheral surface proper of roll 31 does not contact the product Awhen the projections 39 are pressed into 8. and 49. Rolls 48 and 49 eachhave a projecting network comprising two sets of parallel ridges 50 and5| intersecting at right angles. However they may be arranged tointersect at any desired angle I to provide diamond-shaped instead ofsquare or oblong interstices. Roll 49 is also provided with heatingmeans so that activation of the thermoplastic fibers in the web iseffected by such ridges thereby providing the web with a supportingskeletal structure for imparting any predetermined stiffness andrigidity to the web. From rolls 48 and 49, the web passes into the nipbetween rolls 52 and 53. These rolls are provided with complementarysurfaces each comprising pyramidal points 54 in relief ona square basealternating with similar pyramidal depressions 55 in intaglio and anetwork of rectangularly intersecting lines 56 and 51 disposed betweenthe pyramids in an intermediate plane. The rolls are so disposed thatthe network of lines 56 and 51 register substantially with the activatedareas 58 of the web produced by passage through rolls 48 and 49 and sothat the points in relief on roll 52 deform the adjacent unactivatedareas 59 into the .intaglio portions of roll 53 while the relief pointsin roll 53 deform alternate unactivated areas 60 into the intaglio areasof roll 52. The resulting product may be sandwiched between coveringsheets 6| of paper, felt or impermeable material, such as celluloseacetate, Vinylite, and the like to produce a sturdy self-supportingstructure having numerous voids, such as is shown in Figure 8. Thisdeformed structure is also useful for liquid and gaseous filters forobtaining a more highly extended filtration area within a given amountof space.

Activating rolls may have various forms and arrangements of projectionsand certain forms may be especially suitable for particular purposes.

40 For example, the roll 31 in Figure 5 may be rethe mass of the productto the extent desired.

The rolls may be adjusted so that the projections just made contact withthe surface of the fibrous product A or so that they'make anypredetermined pressure upon and penetration into such product.

When a fibrous product of felt-like character is produced in accordancewith the system illustrated in Figure 2, one of the rolls 25 and 26 maybe provided with a suitable pattern in relief and may be heatedinternally to effect activation of the fibrous web in the regionsadjacent the areas corresponding to the elevated lands of the roll in amanner similar to that performed in Figure 5. v

Figure 6 shows a modification in which the fibrous product, especiallyone having a felt-like structure is pressed between a pair of rolls 45and 46 each having a truncated pyramidal projections 41 having a squarebase and arranged with their centers disposed on a system of squares.The heights of the projections are such that the surfaces of the fibrousweb do not come into contact withthe peripheralsurfaces proper of therolls. Both rolls may be, and, preferably are, heated in thisembodiment, so that activation of the thermoplastic fibers is effectedin the regions pressed between the pyramidal'projections.

Figure 7 illustrates another embodiment which is particularly useful fortheproduction of heat and sound insulating. structures. As shown, thefibrous web passes" first between a pair of rolls 48 placed with onehaving a set of parallel peripheral rings to produce a ribbed batteryseparator the structure of which is represented diagrammatically inFigure 9 in which the activated regions comprise narrow strips 62between the highly porous inactivated regions 63. In making a batteryseparator, the fibers employed will of course be of the types that areinert to the acid of the battery; for example the non-adhesive fibersare advantageously mineral fibers, such as spun glass fibers.

Again, the roll 3'! of Figure 5 may be replaced by a roll which isembossed with a design to be impressed upon a pile fabric or a felt likestructure not merely to increase the rigidity of the structure but alsoto impart a decorative effect. Figure 10 illustrates such an embodimentin plan view wherein a design in the form of an activated cross isarranged within an activated border around all four edges of the pieceof material.

It is to be understood that the areas which are not subjected topressure may be activated without pressure as by use of a solvent, steamor dry hot gases, so that such regions have internal strength but ahigher porosity than the compacted areas.

While the drawingillustrates embodiments in which activation is effectedin regions bounded by spaced circular or square areas or a network ofrectangularly intersecting lines, activation may be performed in regionsbounded by areas in the lateral faces of the product of any desiredshape and size. Such regions may be spaced and entirely separate or theymay consist of an intricate pattern or network. ,In eithercase, theyposeor they may serve both purposes. Again, they may be irregular orregular in size, shape,

cordance v with the present invention depends upon the extent ofactivation, the proportion of potentially adhesive fibers in the massand the activation pattern. A preferred embodiment insofar as thetensile strength obtainable is concerned involves the activation along aset of parallel lines which are spaced apart a distance a less than theaverage fiber length in the mass.

Improvement in the tensile strength in two dimensions can beaccomplished by activation along two sets of parallel lines intersectingat right angles and spaced in the manner just described. Instead ofactivating along lines, an improvement in strength can be obtained byactivating at spots or distinct areas which are arranged in parallelrows and are spaced apart by a distance less than the average fiberlength. When such spots are arranged at the corners of a network ofsquares, the diagonal distance is' also preferably made less than theaverage fiber length.

\ In making laminated structures comprising as one layer a fibrous webcontaining potentially adhesive fibers activated locally, advantage maybe taken of the adhesive potentialities of such web in forming a bond atany selected portions of the area of contact or over the entire area ofcontact between such web and the layers adjacent thereto. The bondsbetween laminations may be formed simultaneously with the selectiveactivation of the fibrous web or they may be formed subsequentlythereto.

In the description hereinabove, activation of potentially adhesivefibers in a fibrous web containing them is effected at selected areasonly andsubstantially not at all in the other areas. However, forcertain purposes it is advantageous to effect different degrees ofactivation in the different areas. Thus while a high degree ofactivation and/or compaction is effected in selected areas of the web,none or a lesser but appreciable degree of activation and/or compactionis eifected in some or all of the remaining areas. The difference inactivation may result from the application of different heating effects,different amounts or concentrations of solvents. different pressure, ortwo or more of these factors combined. For example, the projections ofFigure 6 may be made of such height that the peripheral surfaces properof the heated rolls 45 and 46 exert some pressure upon the surfaces ofthe web' when the projections reach their position of maximumpenetration into the web. In this manner, the highly activated areasproduced by the projections are surrounded by the highly porousremaining areas in which a minor but appreciable degree of activationhas been produced by the contact with the peripheral surfaces proper ofthe heated rolls. I

The fibrous products of this invention may be colored before, during, orafter activation, compaction and/or deactivation, for example, bydyeing, or printing, with inks containing pigments of dyestuffs whichare resistant to such treatments. If desired, the activating agent maybe added to the printing ink. For example, in the embodiment of Figures3 and 4, a printing ink comprising a solvent capable of rendering themay be simply decorative or functional in pur- Y arts.

- l potentially adhesive fibers tacky or adhesive may be applied. 1

The felt-like or paper-like fibrous .webs oi the present invention maybe used for many purposes in both the textile and miscellaneousindustrial In the latter, particularly, they may be used as batteryseparators, heat insulation, sound insulation, vibration dampingmaterial, gaskets,

packings, wicks for coating, lubricating, and like purposes, and filtermaterials for gaseous as well as liquid suspensions.

Since certain changes in carrying out the above process, and certainmodifications in the article which embody the invention may be madewithout departing from its scope, it is intended that all mattercontained in the above description or shown'in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

I claim each and every novel and inventive feature shown and describedherein including particularly:

1. As an article of manufacture, a fibrous product comprisingpotentially adhesive fibers substantially uniformly distributedtherethrough,

said product being bonded by fiber-to-fiber ad-' hesion in a group ofpredetermined areas to thereby reinforce the product as a whole and asecond group of areas in the product being bonded to a lesser extent toprovide greater 2. As an article of manufacture, a fibrous productcomprising potentiallly adhesivefibers substantially uniformlydistributed therethrough, said product being bonded by fiber-to-fiberadhesion in a group of predetermined areas to thereby reinforce theproduct as a whole and a second group of areas in the product beingbonded to a lesser extent to provide greater porosity than that of thefirst-mentioned areas, saidproduct having a different density in thefirst-mentioned areas than in the second group of areas, the density andporosity in the second group of areas being substantially uniformthroughout the entire thickness of the product at such areas.

3. As an article of manufacture. a fibrous product comprisingpotentially adhesive fibers substantially uniformly distributedtherethrough, said product being bonded by fiber-to-fiber adhesion in agroup of predetermined areas to thereby reinforce the product as a wholeand a second group of areas in the product being bonded to a lesserextent to provide greater porosity than that of the first-mentionedareas, the density of the product in the first-mentioned areas beinggreater than in the second group of areas, the density and porosity inthe second group of areas being substantially uniform throughout theentire thickness of the product at such areas.

4. As an article of manufacture, a fibrous prodareas being substantiallyuniform throughout the entire thickness of the product at such areas.

CARLETON S. FRANCIS, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Weiss Jan. 18, 1921 Leibing et a1May 11, 1936 Clemens Apr. 30, 1935 Schwartz Aug. 20,1935 Reed May 28,1940 Number 15 Number

